I think a premium site is well worth it if you have a really big rig that is difficult to get into other sites, but otherwise not worth it. From what I've seen, the grills are new (I've never used the grills at the Fort, so that doesn't matter to me), the picnic tables are not new but maybe are repainted (not a big deal, I'm putting a tablecloth on it anyway) and the sites are no bigger, they just have more concrete. That said, I'll pay the extra money to make sure it's mathematically possible to get our 45' motorhome into the site.
We've stayed in the 1400 loop many times, the 200 loop (both of those loops were preferred at the time we were there - not sure what they are now), and the 1000 loop (full hookup at the time), and liked all of them. The 1400 loop was great for its proximity to the pool and the campfire (we didn't think it was too loud - the electrical water parade noise was more annoying), the 1000 loop was great for proximity to the Meadows trading post and pool, and the 200 loop was great for proximity to the Settlement area. I really didn't find any of them to be overly loud, and I'd happily stay at any of them again.